1. Field of the Invention
The present invention relates to an inspection apparatus for liquid crystal display (LCD) panels, and more particularly, to an inspection apparatus for LCD panels which can rapidly inspect for orientation abnormalities of the LCD panels while maintaining the LCD panels at a uniform temperature.
2. Discussion of the Related Art
The growing popularity of various portable electronic products, such as mobile phones, PDAs, notebook computers, and the like, creates demand for lightweight, compact flat panel display devices. Among flat panel display devices, liquid crystal display (LCD) devices, plasma display panel (PDP) devices, field emission display (FED) devices, vacuum fluorescent display (VFD) devices, and the like have been actively developed. Of these, the LCD device is the most popular due to its mass production capability, simple driving mechanism, high definition-capable picture, and the like.
FIG. 1 is a cross-sectional view illustrating a related art liquid crystal display device, and FIG. 2 is a flow diagram illustrating a related art method for manufacturing a liquid crystal display device.
The LCD device is a device that displays information on a screen using refractivity anisotropy.
A related art LCD device denoted by reference numeral 1 includes an upper substrate 3, a lower substrate 5, and a liquid crystal layer 7 between the upper and lower substrates 3 and 5, as illustrated in FIG. 1.
The lower substrate 5 is a substrate having an array of driving components formed thereon. Although not illustrated in FIG. 1, the lower substrate 5 has a plurality of pixels formed thereon, each of which is formed with a driving component such as a thin film transistor. The upper substrate 3 is a substrate for color filters, and has color filter layers for realizing actual color formed therein. In addition, each of the upper and lower substrates 3 and 5 is formed with a pixel electrode and a common electrode, and coated with an orientation film for orientation of liquid crystal molecules in the liquid crystal layer 7.
The upper and lower substrates 3 and 5 are attached by means of a sealing material 9. The liquid crystal layer 7 is disposed between the upper and lower substrates 3 and 5 such that an amount of light transmitting through the liquid crystal layer is controlled by driving the liquid crystal molecules using the driving components arranged on the lower substrate 5, displaying information.
The method for manufacturing the liquid crystal display device generally comprises a driving component array process to form the driving components on the lower substrate 5, a color filter process for forming the color filters on the upper substrate 3, and a cell process. The method for manufacturing the liquid crystal display device will be described in detail with reference to FIG. 2.
First, in the driving component array process, a plurality of gate lines and data lines are arranged to define pixel regions on the lower substrate 5, and each of the pixel regions is then formed with a thin film transistor, which is a driving component connected to the gate lines and the data lines (S101). In addition, a pixel electrode is also formed to connect with the thin film transistor by the driving component array process, such that, when a signal is applied to the pixel electrode via the thin film transistor, the pixel electrode drives the liquid crystal layer.
Subsequently, a common electrode, and color filter layers of R, G and B for exhibiting colors are formed on the upper substrate 3 by the color filter process (S104).
After applying orientation films to the upper and lower substrates 3 and 5, the orientation films are rubbed to supply an orientation regulating force or surface securing force (that is, a pre-tilt angle and orientation) to the liquid crystal molecules in the liquid crystal layer formed between the upper and lower substrates 3 and 5 (S102, S105).
Next, after spacers for maintaining a constant cell gap are scattered on the lower substrate 5, and a sealing material 9 is applied to an outer periphery of the upper substrate 3, the upper and lower substrates 3 and 5 are attached to each other by pressing them together (S103, S106, S107).
Each of the upper and lower substrates 3 and 5 is generally formed of a large size glass substrate. As a result, with the color filter layers and the TFT as the driving component formed in each panel region, a plurality of panel regions are formed on a single large size glass substrate. Thus, it is necessary to cut and process the glass substrate (S108). After the liquid crystal layer is formed by injecting liquid crystals into each processed liquid crystal display panel through a liquid crystal injection port and the liquid crystal injection port is sealed, each liquid crystal display panel is inspected (S109, S110), thus completing manufacturing of the LCD panels.
Inspection of the liquid crystal display panels can be typically divided into appearance inspection, electrical lighting inspection, and orientation abnormality inspection.
The lighting inspection is performed in such a way as to determine whether various electrical components are operating normally by applying a signal to a completed liquid crystal display panel, verifying the results. The appearance inspection is performed in such a way as to determine whether the liquid crystal display panel has an imperfection by inspecting the liquid crystal display panel with naked eyes of an operator. In addition, the orientation abnormality inspection is performed in such a way as to determine whether liquid crystals are gathering or pooling in a lower portion of the liquid crystal display panel that is sagging under its own weight.
The orientation abnormality of liquid crystals is caused by an undesired increase in volume of the liquid crystal layer resulting from the temperature of the liquid crystal layer within the liquid crystal display panel being too high when manufacturing the liquid crystal display panel. This causes the cell gap of the liquid crystal display panel to exceed the height afforded by the spacer. Accordingly, liquid crystals move to the lower portion of the liquid crystal display panel as it sags, making the cell gap become non-uniform, and thereby deteriorating the quality of the liquid crystal display device.
The orientation abnormality inspection is typically performed by observing an image at the lower portion of the liquid crystal display panel with the naked eyes of the operator while light is transmitted through the liquid crystal display panel. That is, if any abnormality is detected in the image during an observation of the lower portion of the liquid crystal display panel, it is determined that there is orientation abnormality in the liquid crystal display panel.
That is, the orientation abnormality inspection is performed in a state in which the completed liquid crystal display panel is maintained at high temperatures. To this end, the orientation abnormality inspection is performed after each liquid crystal display panel is heated in a heating chamber. Heating of the liquid crystal display panels is typically performed in cassettes for inspection efficiency. In other words, after a plurality of liquid crystal display panels are received in a cassette, they are heated to a high temperature in a heating chamber. The heated liquid crystal display panels are conveyed to an inspection apparatus by means of an additional conveying means, and then subjected to the inspection.
However, such a related art inspecting apparatus for detecting orientation abnormality of the LCD panels has a problem in that, because the inspection apparatus is located a predetermined distance away from the heating chamber, the liquid crystal display panels are exposed to surrounding air and are cooled during conveyance to the inspection apparatus after being transferred from the cassette of the heating chamber, thereby making it impossible to perform a precise inspection.
In addition, the related art orientation abnormality inspecting apparatus has a problem in that, because the interior of the heating chamber is exposed to surrounding air while the liquid crystal display panels are transferred from the cassette of the heating chamber, the surrounding air is induced into the heating chamber, causing a non-uniform temperature of the heating chamber.
Furthermore, because the related art orientation abnormality inspecting apparatus requires expensive mechanisms, including a robot for conveying the liquid crystal display panels from the heating chamber to the inspector, manufacturing costs are invariably increased, and a lot of time is required to convey the liquid crystal display panels.